JPH06215887A - Circuit and method for feeding power to high luminance discharge lamp - Google Patents

Abstract

(57) [Abstract] [Objective] In a high-intensity discharge lamp power supply circuit and method, fluctuations in the lamp impedance due to aging of the lamp and the like are compensated to obtain a substantially constant lamp power. [Configuration] A DC bus voltage supply circuit 304 and first and second feedback control circuits are included. The first feedback control circuit 302 is responsive to a first error signal proportional to the difference between the dynamic signal proportional to the peak lamp current and the setpoint signal for the peak lamp current to minimize the error signal. Adjust the bus voltage on the bus current supply conductor. The second feedback control circuit 308 is responsive to a second error signal proportional to the difference between the dynamic signal proportional to the average bus current and the dynamic setpoint signal to ramp the error signal to a minimum. To adjust the power of the lamp. The dynamic setpoint signal is proportional to the difference between the dynamic signal proportional to the regulated bus voltage and the setpoint signal for lamp power.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the field of power supplies for high intensity discharge lamps, and more particularly to power supplies using feedback control to regulate the voltage or current supplied to the lamp. Is.

[0002]

2. Description of the Related Art High pressure sodium lamp (HPSL: hi)
The gh pressure sodium lamp) is an example of a high-intensity discharge lamp, and another example is a quartz mercury lamp. High pressure sodium lamps have been widely used for many years, especially for outdoor lighting applications such as flood lighting and road lighting. One problem with high pressure sodium lamps is that the lamp's aging usually causes the lamp's impedance to drift significantly. Such impedance drift is due to the fact that sodium of the active lamp element is released as a gas into the arc tube containing sodium. The impedance value drifts upwards, and as the lamp is used,
More and more power is required, which eventually exceeds the capacity of the power circuit and the lamp fails.

Variations in impedance from lamp to lamp also result from normal manufacturing tolerances. For example, if the same lamp drive voltage is used, such impedance variations will vary both the lumen output and the wavelength spectrum of the emitted light (ie, the color of the emitted light) from lamp to lamp. Even with the same lamp, changes in line voltage can cause similar variations in lamp characteristics.

One approach to alleviating the above problems is disclosed in US Pat. No. 4,928,038. In this US patent, a power switch is used. When the power switch is on or conducting, a DC bus voltage or compliance voltage is applied across the series combination of the lamp and the driver or ballast inductor. When the switch is off or not conducting,
The lamp is isolated from the bus voltage and thereafter the lamp current is controlled by the impedance of the driver inductor and the internal impedance of the lamp. The average current through the power switch is measured. In the feedback loop, an "error" signal is created that essentially represents the difference between the average switch current and the current setting. The error signal is then used to turn on the power switch to minimize the error signal.
The off operation is controlled. The set value itself may be dynamic, or may be determined according to the fluctuation of the DC bus voltage caused by the fluctuation of the line voltage of the AC power supply.

The approach of US Pat. No. 4,928,038 noted above provides distinct advantages over conventional circuits for powering high pressure sodium lamps, especially in compensating for significant variations in AC line voltage. Was given. However, it is desirable to further improve lamp performance. In particular, it would be desirable to further improve the ability to compensate for significant changes in lamp impedance from lamp to lamp or due to lamp aging.

Further, it is desirable to supply a constant amplitude drive current to the high intensity discharge lamp so as to obtain a reproducible color output.

[0007]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a feedback control circuit and method for powering a high intensity discharge lamp so that the lamp achieves a desired power level even when the lamp impedance value changes significantly. Is to provide. It is another object of the present invention to provide a feedback control circuit and method of the above type which provides a drive current for the lamp with a substantially constant amplitude.

Yet another object is to provide a circuit and method of the above type which can be embodied in low cost, readily available circuit components. The above objective is accomplished by a circuit and method for powering a high intensity discharge lamp according to the present invention. The circuit includes means for supplying a DC bus voltage, and first and second feedback control means. The first feedback control means responds to the first error signal and adjusts the bus voltage on the bus current supply conductor to minimize the first error signal. The first error signal is approximately proportional to the difference between (1) the dynamic signal, which is approximately proportional to the peak bus current, and (2) the setpoint signal for the peak lamp current. The second feedback control means is responsive to the second error signal to drive the lamp with the regulated bus voltage to minimize the second error signal, thereby regulating the power of the lamp. The second error signal is approximately proportional to the difference between (1) a dynamic signal that is approximately proportional to the average bus current and (2) a dynamic setpoint signal. The dynamic setpoint signal is approximately proportional to the difference between (i) a dynamic signal that is approximately proportional to the regulated bus voltage and (ii) a setpoint signal related to lamp power.

The method of the present invention comprises the steps of providing a DC bus voltage and adjusting the bus voltage of the bus current supply conductor in response to the first error signal to minimize the first error signal. Including. The first error signal is approximately proportional to the difference between (1) a dynamic signal that is approximately proportional to the peak lamp current and (2) a setpoint signal for the peak lamp current. The method further includes driving the lamp with a regulated bus voltage in response to the second error signal to minimize the second error signal, thereby regulating the power of the lamp. The second error signal is approximately proportional to the difference between (1) the dynamic signal, which is approximately proportional to the average bus current, and (2) the dynamic setpoint signal. The dynamic setpoint signal is approximately proportional to the difference between (i) a dynamic signal that is approximately proportional to the regulated bus voltage and (ii) a setpoint signal related to lamp power.

The above objects and other advantages of the present invention will be apparent from the following description with reference to the accompanying drawings. The following detailed description of the invention refers to the accompanying drawings.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS To facilitate an understanding of the present invention, first of all, the prior art technique of the above-referenced U.S. Pat. This will be described with reference to FIG. Fig. 1 shows a high pressure sodium lamp (HPSL).
FIG. 3 is a simplified circuit diagram of a circuit for powering a high intensity discharge lamp 100, such as a Sure Sodium Lamp). In the illustrated example, the DC output voltage of the full-wave bridge rectifier 104 is used as the bus voltage V _B , also known as the link voltage or compliance voltage. The current output of full wave bridge rectifier 104 is I _B. AC power is supplied from the power supply 106 to the rectifier 104.
A standard power correction circuit (not shown) may be placed in the current path between the rectifier 104 and the AC power supply 106. The lamp driver circuit 108, which is supplied with the bus voltage V _B and the bus current I _B , “drives” the lamp 100 with the appropriate voltage or current waveform, as described below. Thereby, the lamp power is adjusted toward a constant value.

Feedback generated by the feedback loop shown in FIG.
The lamp driver 108 is controlled by the error signal E.
It In FIG. 2, the low-pass filter 120 has a current I which will be described later.
_SA signal proportional to_SReceive. Where α is proportional
Is a number. The low pass filter 120 is a standard summing amplifier 12
ΑI for positive input of 2_SThe time averaged value of is output. Addition
The negative input of the operational amplifier 122 has a target for the average current.
Value or set value SP ₁Is supplied. This set value SP
₁May be non-dynamic
Yes. The output of the summing amplifier 122 is the gain G of the amplifier 124.
₁Scaled to form the error signal E.
In response to this error signal E, the lamp driver 108
Adjust the uniform lamp power towards a constant value.

FIG. 3 illustrates an enhancement to the feedback loop of FIG. 2 to compensate for variations in the DC bus voltage V _B caused by variations in the line voltage of the AC power supply 106 (FIG. 1). Figure 3
The circuit of FIG. 2 uses the set value SP ₁ used in the feedback loop of FIG. 2 as a dynamic signal. In FIG. 3, signal SP ₁ is the output of standard summing amplifier 140 scaled by gain G ₂ of amplifier 142. The positive input of summing amplifier 140 is the non-dynamic setpoint SP ₂ and the negative input of summing amplifier 140 is the bus voltage V _B scaled by gain G ₃ of amplifier 144.

Details of the lamp driver 108 (FIG. 1) are shown in FIG. As will become apparent later, the circuit of FIG. 4 may include some of the inventive combinations of elements. Therefore, FIG. 4 and the corresponding FIGS. 5 and 6 cannot be said to be prior art. As shown in FIG. 4, the gate control circuit 200 receives the error signal E and receives a power field effect transistor (FET: field-e) of the lamp driver 108.
power switch 2 such as
Control the on (conducting) and off (non-conducting) states of 02. Assuming that the lamp current I _L is initially zero, turning on the power switch 202 causes the lower terminal of the lamp 100 to be grounded via the resistor R. Then, since the initial voltage of the inductor L is zero, the total bus voltage V _B is applied between both terminals of the lamp. The diode D is initially in a non-conducting state. When the switch 202 is turned off, the diode D through a lamp current I _L, then the lamp current I _L decays through inductor L. When the diode D is in a non-conducting state, the current of the power switch 202, that is, the current I _S is common to the bus current I _B, i.e. the same as the bus current I _B. Switch 20
2 is off and diode D is conducting, the current of power switch 202, namely current I _S and bus current I
Both _B are zero. Therefore, in the circuit shown,
Switch current I _S and the bus current I _B is the same.

Switch current I _S (hence bus current I _S
B ) is measured by the resistance R. Through this resistor R,
The switch current I _S flows. The known relationship V = IR, the voltage V _R applied to the upper terminal of resistor R is proportional to the switch current I _S. The voltage V _R is the signal αI _S applied to the low pass filter 120 of FIG. The gate control circuit 200 (FIG. 4) controls the on / off operation of the switch 202 to create the current waveform shown in FIG. In FIG. 5, the solid curve represents the switch current I _S. The solid curve shows a constant duty cycle period T
A train of N trapezoidal pulses 220 in the sequence, followed by a train of N pulses 22 of the next duty cycle period T
2 is included. Below the time axis, the on-off timing cycle for switch 202 is shown.

The first two pulses of the pulse train 220 are
6 is shown. As shown in Figure 6, the switch
When the switch 202 turns on, the beginning of the pulse train 220
Pulse rises from zero to a preset maximum
Line 240). Meanwhile, the switch current is the lamp current I_LWhen
Common, ie lamp current I_LIs the same as. Maximum current
When the value is reached, switch 202 turns off and the switch
Current I_SRapidly drops to zero (curve 242). Shi
Lamp, lamp current I_LThrough the diode D
Attenuates through the L (Fig. 4), and again "I_L"
Follow the sloping dashed curve 244. Switch 202
When turned on again, the switch current I _SIs the curve 246
After a rapid rise along the then common lamp current
I_LRises to maximum along curve 248 with
It That the switch 202 operates cyclically in this way
This produces a train 220 of N pulses.

The next pulse train 222 is shown in FIG. This is also N, but occurs in the period W ₂ shorter than the period W _{1 of} the first pulse train 220. The period W ₂ is shorter because the pulse train 222 is shorter than the pulse train 220.
During this time, the switch 202 is switching at a higher frequency. Since the lengths of the periods W ₁ , W _2, etc. constitute the active part of the duty cycle of a constant period (T) for driving the lamp, such periods W ₁ , W 2
By adjusting the length of _2nd etc., the average current of the lamp is adjusted.

The details of the lamp driver 108 of FIG. 4, and particularly of the gate control circuit 200 therein, are described in the above-referenced US Pat.
28,038, particularly with respect to FIG. 3 of that patent. [Mathematical Analysis of Feedback Loop of US Pat. No. 4,928,038] Referring again to FIG. Power switch 2
In order to control the ON / OFF operation of 02, the lamp power is adjusted toward a constant value as described above. Thus, using the terminology of this application, the above-referenced US Pat. No. 4,928,038 (see, for example, column 3-
4) discloses that the lamp power is essentially proportional to the mathematical product of the DC bus voltage V _B and the switch current I _S (FIG. 4). The DC bus voltage V _B is assumed to be constant for mathematical analysis. This can be expressed mathematically as

[0019]

[Equation 1]

Where P _L is the lamp power, α is the proportional constant, V _B is the bus voltage, and AVE. I _S is switch 2
02 (FIG. 4). According to Equation 1,
By adjusting the average switch current I _S (or common bus current I _B ) towards a constant value, the lamp power tends to be constant. However, the above-mentioned US Pat. No. 4,92
While the 8,038 approach provided a clear improvement in lamp performance, it was found that even further improvements were desirable.
For example, in the present invention, the lamp power is adjusted in a manner that more fully compensates for the impedance that increases over time in lamps such as high pressure sodium lamps.

In accordance with the present invention, FIGS.
Adjusts the power of high-intensity discharge lamp 300 such as an um lamp.
The circuit for adjusting is shown. Full wave bridge rectifier 304
Converts the AC voltage from the AC power supply 306 to DC voltage
And appears between the "+" and "-" output terminals of the rectifier.
It Unlike the prior art FIG. 1, the DC output of the rectifier 304
Bus voltage V between the lamp driver 308 and the lamp driver 308._BAdjustment of
Device 320 is inserted. This V_BThe regulator 320 is a bus
Flow I_BSupply the bus voltage V_BAdjust the value of
Adjust the peak value of the lamp current as shown later. High
In the case of pressure sodium lamps, a nearly uniform lamp color is extremely
Desirable to achieve this uniformity peak lamp
It is known that electric current plays an important role. But
By adjusting this current value,
Lamp color is strongly affected. Furthermore, V_BAdjuster 3
20 is the error signal E₁Feedback controlled by. Error signal
E ₁Is the error signal E supplied to the lamp driver 308.₂
Is another signal. FIG. 8 shows the error signal E₁To generate
A feedback loop for is shown. The beginning of the loop is the lamp current
I_LIs. The current-voltage converter 330 is shown in FIG.
A transformer 400 is included. One of the transformer 400
Lamp current I in the next winding_LFlows, the secondary of the transformer 400
Current αI in the winding_LFlows. Where α is the transformer
The proportional constant of the turns ratio of the secondary winding to the primary winding is shown. Current-electricity
The pressure converter 330 has a conversion gain H.₂To generate output. this
Conversion gain H₂Contains the turns ratio of the above windings
It The output of the converter 330 is further the gain H of the amplifier 332.₁
Peak hold circuit 334 after being scaled by
Reach The output of the peak hold circuit on line 336 is
Current I_LProportional to the peak value of. Standard summing amplifier 3
38. From the output of the peak hold circuit on line 336, set value
SP₁Is subtracted, and the error signal E is output as the output of the adding amplifier.
₁Is obtained.

V _B adjuster 320 responsive to error signal E ₁
(FIG. 7) is shown in more detail in FIG. As shown in FIG. 10, the V _B regulator 320 is a standard ML4
813CP integrated circuit (IC: integrated c)
ircuit) 402 can be used. This is assumed to be used in the following description. IC402
If the above is used as, the summing amplifier 338 of the feedback loop of FIG. 8 is internal to the IC. Therefore,
Pin 8 (P8) of IC402 is line 336 shown in FIG.
The pin 7 (P7) of IC402 corresponds to the summing amplifier 3
Corresponding to 38 negative inputs (FIG. 8). The set value SP ₁ is conveniently provided to pin 7 of IC 402 by the reference voltage V _r . The reference voltage V _r may be non-dynamic. IC40
2 has a standard power factor control (power factor)
A control circuit 404 is also included. The power factor control circuit 404 is responsive to the error signal E1 and its output represents the transformed error signal. This modified error signal is used to control the duty cycle, or on-off operation, of power switch 414. In this way, a power factor control of 0.99 was achieved.

The secondary current flowing through transformer 406 is a regulated bus voltage.
e) REG. Indicate V _B indirectly. The secondary current of the transformer 406 is the regulated bus voltage REG. It is almost proportional to V _B. The reason is that the amount of charge that is “pumped” into capacitor 410 via diode 412 and transformer 406 when switch 414 is off causes capacitor 41 to
0 on the regulated bus voltage REG. This is because the value of V _B is determined. Therefore, according to the timing of the on-off operation of the switch 414, which is determined by the output of the IC 402 on the pin 12 (P12), the adjustment bus voltage REG. V _B
The value of is controlled. Capacitor 410, diode 41
2 and switch 414 together form a standard configuration buck-boost circuit 416. The buck-boost circuit 416 receives the adjusted bus voltage REG. Adjust V _B and, if necessary, RE
G. Raise V _B above the DC bus voltage provided by rectifier 304 (FIG. 3A).

The V _B regulator 320 regulates the regulated bus voltage REG. Supply V _B. As we will see later,
Adjusted bus voltage REG. By supplying V _B , the amplitude of the current used to drive the lamp 300 will be approximately constant. In a high pressure sodium lamp, this consistently causes lamp 300 to exhibit the desired color spectrum. Furthermore V _B regulator 320 compensates for considerable changes in the line voltage of the AC power source 306.

FIG. 9 illustrates the feedback loop used by the lamp driver 308 of FIG. 7 to generate the responsive error signal E ₂ . In FIG. 9, standard summing amplifier 350 receives a negative input from a feedback branch that receives signal I _B 'as an input to current to voltage converter 330'. The average value of the signal I _B 'at least approximates the average bus current I _B. Transducer 330 'the output of the signal I _B' represents those scaled with converter conversion gain H _2. The low pass filter 351 then averages the output of the converter 330 '. This gives the average value to the negative input of summing amplifier 350.

[0026] As an example, the current - voltage converter 330 'signal I _B which undergo' may be the bus current I _B. Figure 4
In this embodiment, the bus current I _B is common with the switch current I _S. The signal I _B 'may be the lamp current I _L.
The average value of the lamp current I _L approximates the average value of the bus current I _B. If the lamp current I _L is input to the converter 330 ′, the converter 330 and the converter 330 ′ of FIG. 8 can be the same.

The input of the amplifier 352 is the regulated bus voltage RE.
G. It may consist of a secondary winding current from transformer 406 (FIG. 10) that is approximately proportional to V _B. As mentioned above, the secondary winding current from transformer 406 is regulated bus voltage REG. V _B
Indirectly. The secondary winding current of transformer 406 is approximately proportional to (N _S / N _P ) (REG.V _B ). here,
REG. V _B is the regulated bus voltage and N _S / N _P is the secondary to primary turns ratio of transformer 406. Amplifier 352
Are preferably configured to receive input current from transformer 406 via an input resistor (not shown) connected to the negative input of an operational amplifier (not shown). At this time,
The input of the operational amplifier is connected to the output of the amplifier via a feedback resistor (not shown). At this time, the gain m of the amplifier 352 is the ratio of the feedback resistance to the input resistance. At this time, the positive input of such an operational amplifier is connected to the MC as described later.
Pins 5 and 1 of IC 470 including 34066P chip
5 (not shown) may be connected. The output of the amplifier 352 is (REG.V _B ) (N _S / N _P ) m. Here, m is the gain of the amplifier 352. Such an output is applied to standard summing amplifier 354 as a negative input.

The positive input of amplifier 354 is the set value SP ₂ . The set value SP ₂ may be non-dynamic. Set value SP
The value of ₂ is referred to herein as K and may be non-dynamic.
The output of summing amplifier 354 is scaled by the gain a of amplifier 356 to obtain the dynamic set point SP ₃ .
This dynamic set value SP ₃ is used as a positive input for the summing amplifier
Applied to. The output of amplifier 350 is the error signal E ₂ . There is typically a so-called offset voltage V _O between the positive and negative inputs of amplifier 350. The value of the offset voltage V _O may be positive or negative. Both setpoints SP ₂ and S of the feedback loop of FIG.
P ₃ is significantly affect the lamp power.

[Mathematical Analysis of the Feedback Loop of the Present Invention] FIG.
A mathematical analysis of the feedback loop shown in and 9 shows, for example, the ability to compensate for significant changes in the impedance Z _L of the lamp 300 (FIG. 7), which is a desirable characteristic for long lamp life. This will be described with reference to the feedback loop shown in FIG. The setpoint SP ₃ can be expressed as follows in the following operation resulting in the input signal of amplifier 352 and SP ₃ .

[0030]

## EQU00002 ## SP ₃ = [K- (REG.V _B ) (N _S / N _P ) m] a (Equation 2) where K is the set value SP ₂ , (REG.V _B ) (N _S /
N _P ) m is the output of amplifier 352 above, and a is the gain of amplifier 356. Using SP ₃ defined in Equation 2, the average lamp current AVE. I _L can be expressed from the feedback loop of Figure 9 as follows.

[0031]

AVE. I _L = (SP ₃ + V _O ) / H ₂ (Equation 3) where AVE. I _L is the average lamp current, H ₂ is the current −
Conversion gain of the voltage converter 330 '(Fig. 9) and V _O, is the offset voltage of the summing amplifier 350.

The power of the lamp 300 (FIG. 7) shall satisfy the following equation.

[0033]

P _L = (AVE.I _L ) (REG.V _B ) (Equation 4) where P _L is the lamp power, AVE. I _L is the average lamp current I _L , and REG. V _B is the regulated bus voltage. More generally, the average lamp current AV in equations 3 and 4
E. I _L is AVE. It can be replaced with I _B '.
Here, AVE. I _B 'at least approximates the average value of the bus current I _B.

AVG. Combining equations 3 and 4 to eliminate the I _L term yields:

[0035]

P _L = [(SP ₃ + V _O ) / H ₂ ] (REG.V _B ) (Equation 5) Adjusted bus voltage REG. V _B can be expressed as:

[0036]

REG. _{V B = (PEAK I L)} [(AVE.Z L) + Z D] , where (Equation 6), PEAK I _L is the peak of the lamp current, AV
E. Z _L is the average frequency dependent impedance of the lamp 300 and Z _D is the impedance of the lamp driver 308.

The peak current PEAK I _L is the set value SP ₁
(FIG. 8) is defined as follows.

[0038]

Equation 7] _{PEAK I L = (SP 1)} / (H 2 H 1) ( Equation 7) where, H ₂ current - gain of the voltage converter 330 (FIG. 8) and H ₁ is an amplifier 332 (FIG, It is the gain of 8).
Combining equations 5, 6 and 7 gives the following equation for lamp power as a function of lamp impedance and parameters of the feedback loop of FIGS. 8 and 9.

[0039]

P _L = [(SP ₁ ) / (H ₂ ² H ₁ )] [(AVE.Z _L ) + Z _D ] (SP ₂ + V _O ) (Equation 8) Combining Equations 2, 6 and 7 As a result, the dynamic set value SP ₃ according to the parameters of the feedback circuit of FIGS.
(FIG. 10) is obtained as follows.

[0040]

SP ₃ = {K − [(SP ₁ ) / (H ₂ H ₁ )] [(AVE.Z _L ) + Z _D ] m (N _S / N _P )} a (Formula 9) where: All terms are as defined above for Equations 2-7. In the equation 9, the dynamic setting value SP ₃ is as shown in FIG.
And that it depends on the parameters of the feedback circuit of FIG. The parameters of the feedback circuit of Figures 8 and 9 are usually constant. Driver impedance Z _D
Is usually constant. Also, the lamp impedance Z
_L changes considerably with age of the high-pressure sodium lamp, that is, over time. Since the set point SP ₃ changes as the lamp impedance changes, the present invention compensates for significant changes in the lamp impedance. FIG. 12 illustrates this graphically.

In FIG. 12, a solid curve 500 plots the relationship between power (watts) and lamp impedance Z _L (ohms). As the high pressure sodium lamp ages, its impedance Z _L increases considerably. By compensating for appreciable changes in the lamp impedance Z _L , the present invention provides a rounded trajectory, shown at 502. This allows the circuit that powers the lamp to supply the required power for a longer time to operate the lamp. Without compensating for the large increase in lamp impedance Z _L , the lamp power-to-impedance curve becomes a continuous trajectory of the dashed curve 504, and it becomes faster that the lamp power supply circuit cannot supply the required power to operate the lamp. .

The error signal E ₂ obtained according to the previous analysis is applied to the lamp driver 308 (FIG. 7). The lamp driver 308 can take the form previously described for FIG. 4 with reference to the corresponding current waveforms of FIGS. A preferred alternative embodiment of the lamp driver 308 is shown in FIG.
0 is shown. In FIG. 10, the lamp driver 308
Is composed of a pair of switches 450 and 452. The on-off operations of switches 450 and 452 are complementary so that switch 450 is off while switch 452 is off.
Is on and switch 4 is off while switch 4
52 is on. Lamp voltage V _L and lamp current I
_L is shown in FIG. If the lamp voltage V _L is initially zero, turning on the switch 450 causes a regulated bus voltage RE across the series combination of the resonant inductor 454, the lamp 300, and the resonant capacitor 456.
G. V _B is applied. At this time, the low impedance of the lamp current detection transformer 400 is ignored. Since the lamp is off at this time, the regulated bus voltage REG. V _B
The whole appears between the ends of the lamp. This sudden rise in the lamp voltage V _L causes the lamp to re-ignite. As a result, the lamp current having a resonance frequency mainly determined by the main inductive element and the capacitive element of the current path starts to flow. The main inductive and capacitive elements of the current path are the resonant inductor 454 and the parallel connected resonant capacitors 456 and 458.

The resonant lamp current I _L causes the lamp voltage V _L to resonate toward 2 (REG.V _B ), and eventually R
EG. It is clamped to the sum of V _B and the voltage drop across one of the diodes 460 and 462.
This point corresponds to π / 2 radians, or 1/4 of the resonance cycle, at which the lamp current (curve 482) reaches its maximum. At this point, the resonant portion of the cycle ends.
The lamp voltage V _L is clamped by one of the diodes 460 and 462 and the energy stored in the inductor 454 is discharged to the bus as an exponential decay.
When the lamp current I _L decays to zero, the switch 450 can be turned off. At this time, the lamp driver 308 is ready to start a cycle in the opposite direction. The common node 465 between the diodes 460 and 462 is the regulated bus voltage REG. This is because the value of V _B is reached.
The length of the "dead time", on the switches 450 and 452 will be described error signal E _2, and later - determined by sensitive circuit for controlling the off operation.

One of the adjusting bus voltage REG. Switch 452 can be turned on with the voltage at node 465 set to the sum of V _B and the voltage drop across one of diodes 460 and 462. Similar to the previous cycle, the REG. The entire V _B is applied and the lamp 300 re-ignites. Upon re-ignition, the lamp current begins to oscillate in the opposite direction to the above current through switch 450. During this time, the lamp voltage _VL is the negative value of the regulated bus voltage -R.
EG. It begins to resonate downwards towards V _B and is eventually clamped to the negative voltage across one of the diodes 460 and 462. At this point, the forced current is at its maximum negative value. As before, the process is the same, only the direction of the current has changed. Standard MC3406 as IC470
When the 6P chip is used, the switches 450 and 452 operate so that the waveform of FIG. 11 is obtained in response to the error signal E ₂ received at the pin 3 (P3). In the following description, it is assumed that a standard MC34066P chip is used as the IC470. Switches 450 and 4
With such operation of 52, the error signal E ₂ is transferred to the transformer 4
It controls the frequency of the signal on the primary winding 471 of 72. Primary winding 471 is connected to output pins 12 and 14 (P
12 and P14) and are polarized as shown. The secondary winding 474 of the transformer 472 is polarized and connected to control the on-off operation of the switch 450. Switch 450 is FE
It can be T. If switch 450 is a FET, secondary winding 474 is connected between the gate and source terminals of that FET. Similarly, another secondary winding 476 is connected with the polarity as shown to control the switch 452. The switch 452 can also be a FET. Since the secondary windings 474 and 476 have opposite polarities, a positive waveform through the primary winding of the transformer 472 turns on only one switch and a negative waveform through the primary winding turns on the other switch only. Let Details of the lamp driver circuit 308 are described in the above-mentioned US patent application No. 971.
No. 806, which is hereby incorporated by reference.

95 Watt High Pressure Sodium Lamp 300
In the case of one possible circuit example of FIG.
To use. That is, the transformer in series with the diode 412
Inductor 406 has an inductance of 172 μHenry,
Capacitor 410 is 470 microfarads, transformer 4
06 N_S/ N_PIs 6/45, and the resonance inductor 454 is
500 microhenry, resonant capacitors 456, 45
8 for 4 microfarads each, IC402 and IC4
70 is the above IC. If you use such a value
Thus, one possible implementation of the feedback loop of FIGS. 8 and 9 is
It looks like this: That is, the gain H₁Is 5.236, profit
Profit H₂Is 80.65 × 10^-3, Set value SP ₁Is 5.0,
Gain m is 95.3 × 10^-3, Set value SP₂(Ie
K) is 5.477, gain a is 14 × 10^-3,offset
Voltage V_OIs 0.

As is apparent from the above description, the present invention is
It compensates for fairly large variations in lamp impedance while maintaining a near constant power level. The invention also supplies the lamp current with a substantially constant amplitude and also allows compensation for fairly large variations in the AC line voltage. Furthermore,
These features can be achieved with low cost and readily available circuit elements. While the particular invention has been illustrated and described, numerous modifications and variations will occur to those skilled in the art. Therefore, the appended claims should be construed to cover all such modifications and variations that fall within the spirit and scope of the invention.

[Brief description of drawings]

FIG. 1 is a block diagram representing a prior art electrical circuit for regulating lamp power.

2 is a block diagram of a portion of a feedback loop used in the circuit of FIG.

3 is a block diagram of a portion of a feedback loop used in the circuit of FIG.

FIG. 4 is a circuit diagram showing in detail the lamp driver circuit shown in block form in FIG.

5 is a waveform diagram showing a waveform of a current in the circuit of FIG.

6 is a waveform chart showing a waveform of a current in the circuit of FIG.

FIG. 7 is a block diagram of an electrical circuit for powering a lamp according to the present invention.

FIG. 8 is a circuit diagram of a feedback loop used in the circuit of FIG.

FIG. 9 is a circuit diagram of a feedback loop used in the circuit of FIG.

10 is a circuit diagram showing in detail a bus voltage adjusting circuit and a lamp driver circuit shown in block form in FIG.

11 is a waveform diagram showing waveforms of current and voltage from the lamp driver circuit of FIG.

FIG. 12 is a graph of lamp power versus lamp impedance in one embodiment of the present invention.

[Explanation of symbols]

300 high-intensity discharge lamp 304 full-wave bridge rectifier 308 lamp driver 320 bus voltage regulator 400 lamp current detection transformer 414 power switch 416 buck-boost circuit 450 switch 452 switch 454 resonant inductor 456 resonant capacitor 458 resonant capacitor 470 IC AVE. I _B Average bus current E ₁ error signal E ₂ error signal REG. V _B Adjusting bus voltage SP ₁ Set value for average current SP ₂ set value SP ₃ set value

Claims (12)

[Claims] 1. A circuit for supplying power to a high-intensity discharge lamp, comprising: (a) a means for supplying a DC bus voltage; (b) minimizing a first error signal in response to the first error signal. The first feedback control means for adjusting the bus voltage on the bus current supply conductor so that the first error signal is (1) a dynamic signal substantially proportional to the peak lamp current, and (2) the peak lamp current. A first feedback control means that is approximately proportional to the difference from the setpoint signal for, and (c) the ramp at an adjusted bus voltage to minimize the second error signal in response to the second error signal. Drive
This is the second feedback control means for adjusting the power of the lamp, wherein the second error signal is (1) the difference between the dynamic signal substantially proportional to the average bus current and (2) the dynamic set value signal. The second feedback control means is substantially proportional to the difference between the dynamic set value signal (i) substantially proportional to the adjusting bus voltage and (ii) the set value signal related to the lamp power. A power supply circuit for a high-intensity discharge lamp, which includes: 2. The second feedback control means applies (a) a regulated bus voltage between both ends of a series circuit including the lamp and the inductor when turned on, and a series bus from the regulated bus voltage when turned off. A high intensity discharge lamp as claimed in claim 1 including a power switch connected in isolation, and (b) switch control means for repeatedly turning the power switch on and off to minimize a second error signal. Power supply circuit. 3. The second feedback control means is configured such that the length of the active portion of the constant cycle duty cycle for driving the lamp is determined by the frequency at which the power switch is repeatedly turned on and off. The power supply circuit for a high-intensity discharge lamp according to claim 2. 4. A buck-boost circuit having a switch whose on-off operation is controlled so as to minimize the first error signal in response to the first error signal, in the first feedback control means. The high-intensity discharge lamp power supply circuit according to claim 1, which is included. 5. The second feedback control means includes: (a) first and second current loops arranged to pass currents through the lamp in first and second opposite directions, respectively. b) first and second power switches for alternating the lamps into the first and second current loops in sequence, and (c) first and second current loops, each loop having its own Includes first and second current loops having inductive and capacitive elements selected such that the current waveform of the loop has a resonant portion that is primarily determined by the values of the inductive and capacitive elements. The power supply circuit for a high-intensity discharge lamp according to claim 1. 6. A method for powering a high intensity discharge lamp comprising: (a) supplying a DC bus voltage; (b) minimizing a first error signal in response to the first error signal. Adjusting the busbar voltage to
The first error signal is (1) a bus signal adjusting step that is substantially proportional to a difference between a dynamic signal that is substantially proportional to the peak lamp current and (2) a set value signal with respect to the peak lamp current, and (c) a second step. Driving the lamp with a regulated bus voltage so as to minimize the second error signal in response to the error signal of
Thus, in the step of adjusting the power of the lamp, the second error signal is proportional to a difference between (1) a dynamic signal substantially proportional to the average bus current and (2) a dynamic set value signal. A dynamic setpoint signal comprises: (i) a lamp driving step that is substantially proportional to a difference between the dynamic signal that is approximately proportional to the regulated bus voltage and (ii) a setpoint signal that is related to lamp power. Power supply method for high-intensity discharge lamp. 7. The lamp driving step comprises: (a) applying a regulated bus voltage across the series circuit including the lamp and an inductor, and then isolating the series circuit from the regulated bus voltage alternately. And (b) controlling the frequency of alternating application of a regulated bus voltage to the series circuit and isolation of the series circuit from the regulated bus voltage so as to minimize a second error signal. The power supply method for the high-intensity discharge lamp according to claim 6. 8. A constant cycle duty cycle for driving the lamp by the step of controlling the frequency of alternating application of a regulated bus voltage to the series circuit and isolation of the series circuit from the regulated bus voltage. The power supply method for a high-intensity discharge lamp according to claim 7, wherein the length of the frequency response of the active portion of the is determined. 9. The step of controlling the on-off operation of a buck-boost circuit whose output is adjusted to minimize the first error signal is included in the step of generating the adjusted bus voltage. Power supply method for high-intensity discharge lamps. 10. The power supply circuit for a high-intensity discharge lamp according to claim 1, wherein the set value signal for the peak lamp current or the set value signal for the lamp power is non-dynamic. 10. The power supply method for a high-intensity discharge lamp according to any one of 9 above. 11. A dynamic signal approximately proportional to the average bus current is determined from the measured current of the lamp.
The power supply circuit for a high-intensity discharge lamp according to claim 1, or the power supply method for a high-intensity discharge lamp according to any one of claims 6 to 9. 12. The lamp driving step comprises alternately alternating the lamps in first and second current loops arranged to pass currents in first and second opposite directions to the lamp, respectively. And each of the first and second current loops is selected such that the current waveform of the loop has a resonant portion that is determined primarily by the values of the inductive and capacitive elements. The power supply method for a high-intensity discharge lamp according to claim 6, further comprising a capacitive element.